/*
 * Copyright 2009 Brendan Kenny
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package gwt.ns.json.client.impl;


/**
 * JSON functionality for browsers without a native implementation. After the
 * JSON object is initialized can be used just like the native implementation.
 * 
 * Code also gracefully hands over control to browser if deferred binding
 * missed something.
 */
public class JsonImplEmulated extends JsonImpl {
	static {
		initEmulatedJSON();
	}
	
	/**
	 * If there is no native JSON functionality, use Douglas Crockford's
	 * json2.js to initialize the JSON object
	 */
	protected static final native void initEmulatedJSON() /*-{
		// NOTE: The code that follows is unmodified from original form except
		// for defining the JSON object on $wnd
		
		// http://www.JSON.org/json2.js
		// 2010-03-20
		// Public Domain.
		// NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
		// See http://www.JSON.org/js.html
		// This is a reference implementation. You are free to copy, modify, or
		// redistribute.

		// Create a JSON object only if one does not already exist. We create the
		// methods in a closure to avoid creating global variables.
		if (!$wnd.JSON) {
			$wnd.JSON = {};
		}

		(function () {

			function f(n) {
				// Format integers to have at least two digits.
				return n < 10 ? '0' + n : n;
			}
	
			if (typeof Date.prototype.toJSON !== 'function') {
				Date.prototype.toJSON = function (key) {
		
				    return isFinite(this.valueOf()) ?
				           this.getUTCFullYear()   + '-' +
				         f(this.getUTCMonth() + 1) + '-' +
				         f(this.getUTCDate())      + 'T' +
				         f(this.getUTCHours())     + ':' +
				         f(this.getUTCMinutes())   + ':' +
				         f(this.getUTCSeconds())   + 'Z' : null;
				};
		
				String.prototype.toJSON =
				Number.prototype.toJSON =
				Boolean.prototype.toJSON = function (key) {
				    return this.valueOf();
				};
			}
	
			var cx = /[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g,
			escapable = /[\\\"\x00-\x1f\x7f-\x9f\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g,
			gap,
			indent,
			meta = {    // table of character substitutions
			    '\b': '\\b',
			    '\t': '\\t',
			    '\n': '\\n',
			    '\f': '\\f',
			    '\r': '\\r',
			    '"' : '\\"',
			    '\\': '\\\\'
			},
			rep;
	
	
			function quote(string) {
				// If the string contains no control characters, no quote characters, and no
				// backslash characters, then we can safely slap some quotes around it.
				// Otherwise we must also replace the offending characters with safe escape
				// sequences.
		
				escapable.lastIndex = 0;
				return escapable.test(string) ?
				    '"' + string.replace(escapable, function (a) {
				        var c = meta[a];
				        return typeof c === 'string' ? c :
				            '\\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
				    }) + '"' :
				    '"' + string + '"';
			}
	
	
			function str(key, holder) {
				// Produce a string from holder[key].
				
				var i,          // The loop counter.
				    k,          // The member key.
				    v,          // The member value.
				    length,
				    mind = gap,
				    partial,
				    value = holder[key];
		
				// If the value has a toJSON method, call it to obtain a replacement value.
				if (value && typeof value === 'object' && typeof value.toJSON === 'function') {
					value = value.toJSON(key);
				}
		
				// If we were called with a replacer function, then call the replacer to
				// obtain a replacement value.
				if (typeof rep === 'function') {
					value = rep.call(holder, key, value);
				}
		
				// What happens next depends on the value's type.
				switch (typeof value) {
				case 'string':
				    return quote(value);
		
				case 'number':
					// JSON numbers must be finite. Encode non-finite numbers as null.
				    return isFinite(value) ? String(value) : 'null';
		
				case 'boolean':
				case 'null':
					// If the value is a boolean or null, convert it to a string. Note:
					// typeof null does not produce 'null'. The case is included here in
					// the remote chance that this gets fixed someday.
				    return String(value);
		
				// If the type is 'object', we might be dealing with an object or an array or
				// null.
				case 'object':
					// Due to a specification blunder in ECMAScript, typeof null is 'object',
					// so watch out for that case.
				    if (!value) {
				        return 'null';
				    }
		
					// Make an array to hold the partial results of stringifying this object value.
				    gap += indent;
				    partial = [];
		
					// Is the value an array?
				    if (Object.prototype.toString.apply(value) === '[object Array]') {
		
					// The value is an array. Stringify every element. Use null as a placeholder
					// for non-JSON values.
				        length = value.length;
				        for (i = 0; i < length; i += 1) {
				            partial[i] = str(i, value) || 'null';
				        }
		
					// Join all of the elements together, separated with commas, and wrap them in
					// brackets.
				        v = partial.length === 0 ? '[]' :
				            gap ? '[\n' + gap +
				                    partial.join(',\n' + gap) + '\n' +
				                        mind + ']' :
				                  '[' + partial.join(',') + ']';
				        gap = mind;
				        return v;
				    }
		
					// If the replacer is an array, use it to select the members to be stringified.
				    if (rep && typeof rep === 'object') {
				        length = rep.length;
				        for (i = 0; i < length; i += 1) {
				            k = rep[i];
				            if (typeof k === 'string') {
				                v = str(k, value);
				                if (v) {
				                    partial.push(quote(k) + (gap ? ': ' : ':') + v);
				                }
				            }
				        }
				    } else {
		
						// Otherwise, iterate through all of the keys in the object.
				        for (k in value) {
				            if (Object.hasOwnProperty.call(value, k)) {
				                v = str(k, value);
				                if (v) {
				                    partial.push(quote(k) + (gap ? ': ' : ':') + v);
				                }
				            }
				        }
				    }
		
					// Join all of the member texts together, separated with commas,
					// and wrap them in braces.
				    v = partial.length === 0 ? '{}' :
				        gap ? '{\n' + gap + partial.join(',\n' + gap) + '\n' +
				                mind + '}' : '{' + partial.join(',') + '}';
				    gap = mind;
				    return v;
				}
			}
	
			// If the JSON object does not yet have a stringify method, give it one.
			if (typeof $wnd.JSON.stringify !== 'function') {
				$wnd.JSON.stringify = function (value, replacer, space) {
		
					// The stringify method takes a value and an optional replacer, and an optional
					// space parameter, and returns a JSON text. The replacer can be a function
					// that can replace values, or an array of strings that will select the keys.
					// A default replacer method can be provided. Use of the space parameter can
					// produce text that is more easily readable.
				    var i;
				    gap = '';
				    indent = '';
		
					// If the space parameter is a number, make an indent string containing that
					// many spaces.
				    if (typeof space === 'number') {
				        for (i = 0; i < space; i += 1) {
				            indent += ' ';
				        }
		
					// If the space parameter is a string, it will be used as the indent string.
				    } else if (typeof space === 'string') {
				        indent = space;
				    }
		
					// If there is a replacer, it must be a function or an array.
					// Otherwise, throw an error.
				    rep = replacer;
				    if (replacer && typeof replacer !== 'function' &&
				            (typeof replacer !== 'object' ||
				             typeof replacer.length !== 'number')) {
				        throw new Error('JSON.stringify');
				    }
		
					// Make a fake root object containing our value under the key of ''.
					// Return the result of stringifying the value.
				    return str('', {'': value});
				};
			}
	
	
			// If the JSON object does not yet have a parse method, give it one.
			if (typeof $wnd.JSON.parse !== 'function') {
				$wnd.JSON.parse = function (text, reviver) {
		
					// The parse method takes a text and an optional reviver function, and returns
					// a JavaScript value if the text is a valid JSON text.
				    var j;
		
				    function walk(holder, key) {
						// The walk method is used to recursively walk the resulting structure so
						// that modifications can be made.
		
				        var k, v, value = holder[key];
				        if (value && typeof value === 'object') {
				            for (k in value) {
				                if (Object.hasOwnProperty.call(value, k)) {
				                    v = walk(value, k);
				                    if (v !== undefined) {
				                        value[k] = v;
				                    } else {
				                        delete value[k];
				                    }
				                }
				            }
				        }
				        return reviver.call(holder, key, value);
				    }
		
		
					// Parsing happens in four stages. In the first stage, we replace certain
					// Unicode characters with escape sequences. JavaScript handles many characters
					// incorrectly, either silently deleting them, or treating them as line endings.
					text = String(text);
				    cx.lastIndex = 0;
				    if (cx.test(text)) {
				        text = text.replace(cx, function (a) {
				            return '\\u' +
				                ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
				        });
				    }
		
					// In the second stage, we run the text against regular expressions that look
					// for non-JSON patterns. We are especially concerned with '()' and 'new'
					// because they can cause invocation, and '=' because it can cause mutation.
					// But just to be safe, we want to reject all unexpected forms.
			
					// We split the second stage into 4 regexp operations in order to work around
					// crippling inefficiencies in IE's and Safari's regexp engines. First we
					// replace the JSON backslash pairs with '@' (a non-JSON character). Second, we
					// replace all simple value tokens with ']' characters. Third, we delete all
					// open brackets that follow a colon or comma or that begin the text. Finally,
					// we look to see that the remaining characters are only whitespace or ']' or
					// ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.
				    if (/^[\],:{}\s]*$/.
					test(text.replace(/\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g, '@').
					replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, ']').
					replace(/(?:^|:|,)(?:\s*\[)+/g, ''))) {
		
						// In the third stage we use the eval function to compile the text into a
						// JavaScript structure. The '{' operator is subject to a syntactic ambiguity
						// in JavaScript: it can begin a block or an object literal. We wrap the text
						// in parens to eliminate the ambiguity.
				        j = eval('(' + text + ')');
		
						// In the optional fourth stage, we recursively walk the new structure, passing
						// each name/value pair to a reviver function for possible transformation.
				        return typeof reviver === 'function' ?
				            walk({'': j}, '') : j;
				    }
		
					// If the text is not JSON parseable, then a SyntaxError is thrown.
				    throw new SyntaxError('JSON.parse');
				};
			}
		}());
	}-*/;
}
